This invention pertains to a method of sealing an electron gun mount in a cathode-ray tube.
In manufacturing a cathode-ray tube comprising a panel assembly with a phosphor screen, a funnel-shaped back section having a neck, and a mount containing an electron gun, the back section typically is sealed to a faceplate panel of the panel assembly using a glass frit before the mount is sealed to the neck of the funnel-shaped back section. Since the frit-sealing step is performed in a high-temperature oven or lehr at a temperature of about 450.degree. C., it is desirable that the electron gun not be subjected to this heating step in order to prevent the cathode of the gun from being oxidized and exposed to contamination originating from the heated glass frit. Therefore, the mount is sealed to the neck of the back section after the frit-sealing step by a flame-sealing apparatus which applies a 1,000.degree. C. torch only to a localized area around the neck where the seal is to be formed. Exhausting and a final tubulation seal are then performed.
In order to improve the focusing capability of the cathode-ray tube and also make the tube as thin as possible, the mount containing the electron gun must be positioned closer to the phosphor screen. The geometrical considerations for the design of such a thin tube require a differently shaped back section which may not include a neck capable of being flame sealed, thereby precluding the feasibility of utilizing the aforementioned mount-sealing step wherein a torch is applied to the neck. The present invention provides a method of sealing the mount of the cathode-ray tube to the back section thereof during the frit-sealing step, thereby achieving a thinner tube.